The invention relates to an integrated turboramjet engine having a common air inlet for the turbo and the ramjet circuit, having an annular turbo-inlet duct and a ram-air inlet duct which surrounds it concentrically.
Endeavors are taking place to develop hypersonic airplanes which can take off and land on normal airfields and develop cruising speeds of several Mach. Hypersonic airplanes of this type may be used either as fast long-distance transport planes or as normally starting space tugs. The achievable Mach numbers range between Mach 4 and 8 at flight altitudes of approximately 30 km.
Engines for the propulsion of such airplanes must meet a number of requirements which cannot be met by means of conventional engine concepts. Thus, on the one hand, a sufficient power output must take place at low flying speeds of below Mach 1 up to the top speeds. For this purpose, it has been suggested to provide combined turboramjet engines which, at low flying speeds, operate as gas turbine jet engines with or without an afterburner and, above a certain flying speed, operate as ramjet engines (RAM operation).
An embodiment of such engines provides that a gas turbine engine is provided on both sides with flaps that can be shut, an afterburner flow starting from the gas turbine, at the same time, being used as the ramjet combustion chamber. For this purpose, an annular ram air duct is provided concentrically outside the gas turbine through which the inflowing air, during the ramjet operation, is guided directly into the combustion chamber while bypassing the gas turbine. For this purpose, movable guide plates are provided in the area of the inlet duct and behind the turbine which selectively guide the air flow either in the concentrically interior turbo-inlet duct and thus through the gas turbine core engine, or into the concentrically exterior ram-air inlet duct.
It is a serious problem in the case of such change-over engines that the outer diameter of the engine must be kept as small as possible in order to, on the one hand, keep the flow resistances caused by the airplane as low as possible and, on the other hand, in the case of a suggested mounting of a row of approximately 5 engines next to one another, achieve an overall width that is as small as possible. The minimum extent of the outside diameter of the engine is determined by the cross-sections of the two inlet ducts as well as the inside diameter required in the hub area for the core engine.
Based on the above, it is an object of the present invention to construct a turboramjet engine such that a deflection of the air current is possible into one of the two inlet ducts, in which case the minimum outside diameter of the engine given by the aerodynamic and constructive parameters must be exceeded as little as possible.
According to the invention, this object is achieved by an integrated turboramjet engine having a common air inlet for the turbo and for the ramjet circuit, having an annular turbo-inlet duct and a ram-air inlet duct which concentrically surrounds this turbo-inlet duct, and having a conical guide ring which is stationarily arranged in the air inlet and radially inside of which an inlet cone is provided and radially outside of which a lock ring is provided which can axially slide against the inlet cone,
wherein said inlet cone and lock ring are selectively adjustable between a first ramjet operating position with the inlet cone situated in its front end position and the lock ring situated in its rear end position so that the inlet cone, guide ring and lock ring form a duct wall which guides the gas flow into the ramjet inlet duct and, a second ramjet operating position with the ram-air inlet duct being closed off by the lock ring and the gas flow being guided on both sides of the guide ring into the turbo-inlet duct.
It is a principal advantage of the invention that, while the minimum diameter defined by the inlet ducts is maintained, a deflection of the air current is possible into one of the two inlet ducts, in which case a low-loss wall contour of the flow ducts can be achieved at the same time. In addition, by means of this arrangement, also at the critical moment of the change-over from the turbo to the ramjet operation, the engine power can be maintained because of the fact that the arriving air can be deflected in a targeted and continuous manner from one inlet duct into the other inlet duct.
Advantageously, only two movable parts, specifically the inlet cone and the lock ring must be constructed to be movable with respect to one another by means of simple adjusting drives. These movable parts are constructed to be rotationally symmetrical and may therefore have an advantageous construction with respect to their weight. This type of a rotationally symmetrical construction is also suitable for the film cooling or convective cooling in the ramjet operation.
Another advantage is the fact that, in the ramjet operation, driving and guiding elements of the movable parts are housed in the closed-off turbo-part and are covered. The strokes of these parts may be kept short and approximately identical for both parts. As a result, a synchronization of the movements and an improvement of the change-over function can be achieved. It is also an advantage that the whole shut-off system takes up only a short length and requires a low weight.
Good sealing possibilities of the moving parts, that is the inlet cone and the lock ring, exist with respect to the stationary parts, that is, the outer wall and the guide ring. In addition, only low adjusting forces are required for the adjustment of these movable parts in all operating conditions and also in the case of high back pressures.
Finally, it is an advantage that the whole shut-off arrangement is constructed in a modular design and can therefore be integrated between the air inlet housing and the engine housing.
The contour of the stationary guide ring is preferably constructed such that the dividing of the approaching air takes place uniformly into the two concentric flow ducts radially inside and outside the guide ring and, in the process, a uniform acceleration of the flow is achieved with a uniform flow profile existing over the whole flow cross-section. As a result, a uniform inflow is achieved by way of a gooseneck-shaped flow duct with a corresponding acceleration in the direction of the compressor.
In an advantageous further development of certain preferred embodiments of the invention, the guide ring, by means of a number of radial supporting ribs, is supported on the interior housing of the engine. This arrangement has the advantage that no components are situated in the flow duct during the ramjet operation and the resulting high temperatures.
Another advantageous development of certain preferred embodiments of the invention provides that the exterior wall of the ram air inlet duct has a square cross-section in the moving range of the lock ring. This arrangement has the significant advantage that, during the ramjet operation, the corner areas of the square housing can also be used for the introduction of air into the ram air inlet duct, resulting in smaller outer dimensions of the engine. In comparison to a construction with a rotationally symmetrical outer wall, the circular duct radially outside the lock ring may advantageously be eliminated which means that the outer wall which has a square cross-section is pulled toward the inside until it reaches the lock ring.
A further development of this construction provides that the air inlet housing has a square construction and is deformed into a round cross-section in a transition area downstream of the rear end position of the lock ring, in which case an air-guiding shell is mounted upstream of the lock ring on the inside at the air inlet housing which, up to its contact line with the lock ring, has a transition from the square to the round cross-section, and in its further course, adapts itself again from a round shape to a square shape with respect to the air inlet housing. In connection with the lock ring, this results in a favorable flow contour from the air inlet to the compressor inlet (gooseneck) as well as to the ram air inlet duct. A significant advantage of this construction is achieved by the fact that, when several engines are arranged next to one another, the air inlets have a rectangular cross-section which up to now upstream of this change-over arrangement, had been changed to a round cross-section. By means of the solution according to the invention, it is therefore possible to retain this rectangular contour up to far toward the rear and utilize it at the same time for the change-over of the air flow.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.